Currently, rheological behaviors of fluids and characteristic parameters thereof are mainly measured by rheometers. The main object of a commercial rheometer is to test rheological behaviors of a medium, to optimize parameters of the medium in different operation conditions, and to verify a rheological constitutive equation theory. Traditional rheometers include capillary type rheometer, rotating rheometer, oscillating rheometer, stable state rheometer, and solid state rheometer. However, an existing rotation rheometer generally has a highest rotation speed of 5000 rpm, and a shearing rate thereof is hard to achieve 1×104/s. Although a capillary type rheometer may have a shearing rate up to about 1×104/s, it cannot test influences of different surfaces on the movements. Therefore, both rheometers cannot test in high shearing rate conditions. The ultra-shear viscometer from PCS company may measure shearing rates ranging from 1×106/s to 1×107/s, however, it cannot measure viscosities under relatively lower shearing rate conditions. Consequently, a rheometer having a relatively wider measuring range and being accurate at high shearing rates is needed.
The measuring method of a traditional rheometer generally uses stress-strain sensors or torque motors, which is limited by the accuracy of the sensor and has relatively lower measuring accuracy and relatively narrower measuring range, for example, two or three orders of magnitude. The gap control of a conventional rheometer is generally achieved by using a motor, which not only has large noise, but also has low control accuracy. Worse still, relatively smaller gaps are hard to obtain.